1. Field of the Invention
This invention relates to static wheel balancers for determining the balance of vehicle wheels, and more particularly, it relates to static wheel balancers of the type having a pivot mounting for supporting a wheel balancing head upon a vertical support post.
2. Description of the Prior Art
The principle of a common type of static wheel balancer is in itself a simple one. The wheel (with a mounted tire) is placed on a wheel balancing head mounting a bubble level for balancing. The head is supported by a pivot mechanism, usually a hard steel ball or sphere which rests on the anvil of a post or other vertical support means coaxial with the wheel and balancing head. If the wheel to be balanced is out of balance, the wheel balancing head will tilt about an axis in a horizontal plane, and this tilt will manifest itself by an off-center reading on the bubble level. The balance error is usually corrected by the application of one or more balance weights to the rim flange of the wheel. Balancers of this type subject the pivot ball and supporting structure to shock loads in cases where a heavy wheel and tire assembly are initially dropped onto the balancing head, and special means are often provided to protect the ball from these loads.
The U.S. Pat. No. 3,055,221, issued Sept. 25, 1922 to Bageman et al, discloses a static wheel balancer of the afore-described type having a vertical support post or pedestal formed with a flat faced tappet or anvil. The balancing head is pivotally supported on the anvil by a pivot ball rigidly mounted in the balancing head. A cam mechanism is provided to lower the anvil so that the balance head rests on a support sleeve when the wheel is placed on the head.
A similar pivot ball and anvil construction for supporting the balancing head is shown in U.S. Pat. No. 3,164,996, issued Jan. 12, 1965 to Carrigan and assigned to the FMC Corporation. This patent also shows structure for lowering the anvil during wheel application. Furthermore, in this patent, the wheel centering cone of the balancing head is resiliently supported to minimize damage to the pivot ball and the supporting anvil from impacts that occur when a wheel assembly is dropped onto the balancing head.
The U.S. Pat. No. 3,280,640, issued Oct. 25, 1960 to Fuertges, also employs a single, rigidly mounted pivot ball supported on an anvil. The anvil post is slidably mounted in a support sleeve and the post is initially supported by a spring. When the wheel is placed on the balancing head, the post is lowered against the force of the spring until the lower end of the post is solidly seated on a shoulder. Oil bleed holes, valved by the post, are provided in the sleeve to control deceleration of the post.